Causes of diaper rash (nappy rash)

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Diaper rash (also known as nappy rash occurs when your baby's skin comes into contact with urine and faeces usually for prolonged periods of time. There are many factors in addition that play a role in causation of diaper rash (also called diaper dermatitis in medical parlance).

The causes and aetiology of diaper rash include wetness, friction and so forth. 1-5

Wetness and diaper rash

Wetness is the commonest culprit behind diaper rash. Being soiled the nappy fails to absorb the expelled waste fluids completely. This causes the nappy to remain wet when it contact with the baby’s skin around the nappy area.

The wetness leads to destruction of the skin barrier and its penetration by irritants present in urine and faeces becomes easier.

Friction and diaper rash

Friction plays another important role in diaper rash. Constant rubbing and vigorous rubbing against the soft skin around the nappy area by the nappy may give rise to nappy rash.

Urine and faeces and diaper rash

The faeces contain enzymes like proteases and lipases. These enzymes act on the urine to release irritant chemical called ammonia. This raises the pH of the area within the nappy and skin irritation occurs.

Microorganisms - fungal, bacterial and viral infections and diaper rash

Fungal infections like Candida albicans is seen in up to 80% of infants with skin irritation around the nappy area. The area is damp and wet and this leads to breakdown of the skin barriers and commonly within 48-72 hours after irritation the infection occurs.

In babies who are already on antibiotics there is a risk of destruction of healthy good bacteria living in the nappy areas. This leads to increased likelihood of fungal infections.

Babies with diabetes, suppressed immunities with conditions like HIV/AIDS infection and other disease also have an increased risk of fungal infections around the diaper areas. Tinea (ring worm) is another fungal infection that may affect babies in their diaper areas.

Bacteria like Staphylococcus aureus or group A streptococci can also lead to eruptions in the diaper area. Staph infection is more common in children who have a tendency to develop skin allergies (atopic dermatitis).

These infections often go on to affect the vulva, vagina and surrounding tissues (vulvovaginitis) in female babies. This could lead to life threatening complications. Other bacteria include Shigella, Escherichia coli, and Yersinia enterocolitica.

Viruses like coxsackie, herpes simplex, human immunodeficiency viruses and parasites like pinworms, scabies may also lead to rash in the diaper area.

Nutrition and diaper rash

Babies lacking in biotin and Zinc in their diet are also likely to get diaper rash.

Chemical irritants and diaper rash

Harsh soaps, fragrances, preservatives, powders, oils, detergents (in which cloth nappies have been washed) and antiseptics often cause irritation of the soft skin around the nappy area and may lead to diaper rash.

Diarrhoea and diaper rash

Diarrhoea in the baby leads to frequent liquid faeces. Since the food passes undigested there is a large amount of residual digestive enzymes in these loose stools. These may lead to irritation around the anus and diaper rash.

Developmental abnormalities of the urinary tract and risk of diaper rash

In babies with anatomical defects of the urinary passage that leads to constant of frequent dribbling of urine also have a raised risk of diaper rash.

Eczema and diaper rash

Eczema is a skin condition that makes the baby’s skin dry and sore. This may be more widespread around the body. A family history of eczema and nappy rash despite skin care should alert for eczema as a cause for diaper rash.

Seborrhoeic dermatitis and diaper rash

Seborrhoeic dermatitis (also called cradle’s cap) leads to red, scaly skin in babies aged between two weeks and six months. It is commonly seen over the scalp, ears, eyebrows, armpit and neck. Sometimes it may also affect the nappy area.

Other conditions that may lead to a rash around the diaper area

Other disease conditions like psoriasis, Granuloma gluteale infantum, Letterer-Siwe disease, Cystic fibrosis and Kawasaki’s disease may all lead to rash around the diaper area.

Further Reading

Last Updated: May 29, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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